ナレッジハブ・技術ガイド
画像リサイズ・解像度とアスペクト比計算ガイド
画像リサイズ・解像度とアスペクト比計算ガイド
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コアアーキテクチャ & 計算式
New Height = (Original Height / Original Width) * New Width
To prevent your images from looking squished or stretched, you must lock the Aspect Ratio. The formula calculates the exact proportional height based on your desired width.
ベストプラクティスとガイドライン
- Never Scale Up (Upsample): Raster images (like JPEG or PNG) are made of fixed pixels. Scaling a 500px image up to 1000px forces the browser to guess missing pixels, resulting in a blurry, pixelated mess.
- Serve Responsive Images: Don't just generate one size. Generate multiple sizes (e.g., 400px, 800px, 1200px) and use the HTML `srcset` attribute to let the browser download the optimal size for the user's screen.
- Crop Before Resizing: If the subject of your photo is tiny, crop the image tightly around the subject first. Resizing an uncropped image will just make the subject even smaller.
よくある質問 (FAQ)
What is an Aspect Ratio?
An aspect ratio is the proportional relationship between width and height. Standard widescreen video is 16:9, traditional photos are 3:2, and Instagram posts are usually 1:1 (square).
Does resizing an image reduce its file size?
Drastically. Reducing an image's dimensions from 4000px to 1000px eliminates millions of pixels, exponentially decreasing the final file size in megabytes.
What interpolation method is used?
Modern web browsers automatically apply high quality bicubic or bilinear interpolation algorithms when scaling images down via the Canvas API, ensuring smooth edges.